The present invention relates to a device for intrabody delivery of molecules, to a method and system of utilizing same and to a method of fabricating same. More particularly, embodiments of the present invention relate to a drug delivery device which utilizes an acoustic transducer for generating an electrical activation signal from an acoustic signal received thereby.
The efficacy of drug treatment is oftentimes dependent upon the mode of drug delivery.
Localized drug delivery is oftentimes preferred since it traverses limitations associated with systemic drug delivery including rapid drug inactivation and/or ineffectual drug concentrations at the site of treatment. In addition, in some cases, systemic drug delivery can lead to undesired cytotoxic effects at tissue regions other than that to be treated.
Since localized intrabody delivery of medication is central to efficient medical treatment, attempts have been made to design and fabricate intrabody delivery devices which are capable of controlled and localized release of a wide variety of molecules including, but not limited to, drugs and other therapeutics.
Controlled release polymeric devices have been designed to provide drug release over a period of time via diffusion of the drug out of the polymer and/or degradation of the polymer over the desired time period following administration to the patient. Although these devices enable localized drug delivery, their relatively simple design is limited in that it does not enable accurate and controlled delivery of the drug.
U.S. Pat. No. 5,490,962 to Cima, et al. discloses the use of three dimensional printing methods to make more complex devices which provide release over a desired time frame, of one or more drugs. Although the general procedure for making a complex device is described, specific designs are not detailed.
U.S. Pat. No. 4,003,379 to Ellinwood describes an implantable electromechanically driven device that includes a flexible retractable walled container, which receives medication from a storage area via an inlet and then dispenses the medication into the body via an outlet.
U.S. Pat. Nos. 4,146,029 and 3,692,027 to Ellinwood disclose self-powered medication systems that have programmable miniaturized dispensing means.
U.S. Pat. No. 4,360,019 to Jassawalla discloses an implantable infusion device that includes an actuating means for delivery of the drug through a catheter. The actuating means includes a solenoid driven miniature pump.
Since such devices include miniature power-driven mechanical parts which are required to operate in the body, i.e., they must retract, dispense, or pump, they are complicated and subject to frequent breakdowns. Moreover, due to complexity and size restrictions, they are unsuitable for delivery of more than a few drugs or drug mixtures at a time.
U.S. Pat. Nos. 6,123,861 and 5,797,898 both to Santini, Jr., et al. disclose microchip devices which control both the rate and time of release of multiple chemical substances either in a continuous or a pulsatile manner. Such microchip devices employ a reservoir cap which is fabricated of a material that either degrades or allows the molecules to diffuse passively out of the reservoir over time or materials that oxidize and dissolve upon application of an electric potential. Release from the microchip device can be controlled by a preprogrammed microprocessor, via a radiofrequency (RF) activation signal, or by biosensors.
Although the microchip device described by Santini, Jr., et al. presents substantial improvements over other prior art devices, it suffers from several inherent limitations which will be described in detail hereinbelow.
There is thus a widely recognized need for, and it would be highly advantageous to have, a delivery device and methods of fabricating and utilizing same which device can be used for accurate and timely delivery of a drug or drugs within a body tissue region devoid of the above limitation.
The present invention also relates to an acoustic transducer and, in particular, to a miniature flexural piezoelectric transducer for receiving acoustic energy transmitted from a remote source and converting such energy into electrical power for activating an electronic circuit. Further, the present invention relates to a miniature flexural piezoelectric transmitter for transmitting acoustic information by modulating the reflection of an external impinging acoustic wave.
The prior art provides various examples of piezoelectric transducers. Examples of such piezoelectric transducers are disclosed in U.S. Pat. Nos. 3,792,204; 4,793,825; 3,894,198; 3,798,473; and 4,600,855.
However, none of the prior art references provide a miniature flexural piezoelectric transducer specifically tailored so as to allow the usage of low frequency acoustic signals for vibrating the piezoelectric layer at its resonant frequency, wherein substantially low frequency signals herein refer to signals having a wavelength that is much larger than the dimensions of the transducer. Further, none of the prior art references provide a miniature transducer having electrodes specifically shaped so as to maximize the electrical output of the transducer. Further, none of the above references provide a transducer element which may be integrally manufactured with any combination of electronic circuits by using photolithographic and microelectronics technologies.
Further, the prior art fails to provide a miniature flexural piezoelectric transmitter which modulates the reflected acoustic wave by controllably changing the mechanical impedance of the piezoelectric layer according to a message signal received from an electronic component such as a sensor. Further, the prior art fails to provide such transmitter wherein the piezoelectric layer is electrically connected to a switching element, the switching element for alternately changing the electrical connections of the transmitter so as to alternately change the mechanical impedance of the piezoelectric layer. Further, the prior art fails to provide such transducer wherein the mechanical impedance of the piezoelectric layer is controlled by providing a plurality of electrodes attached thereto, the electrodes being electrically interconnected in parallel and anti-parallel electrical connections. Further, the prior art fails to provide such transmitter wherein the piezoelectric layer features different polarities at distinct portions thereof. Further, the prior art fails to provide such transmitter which includes a chamber containing a low pressure gas for enabling asymmetrical fluctuations of the piezoelectric layer. Further, the prior art fails to provide such transmitter having a two-ply piezoelectric layer.